Depending on materials of an active layer, TFT mainly includes an oxide semiconductor TFT (oxide TFT for short) and an a-Si (amorphous silicon) TFT. The oxide TFT is more suitable for manufacturing a high-end product with a high resolution (high definition) and a high refresh rate (a smooth dynamic image) due to a large on/off current ratio (i.e., a situation where a current is larger and a charging time is shorter when the oxide TFT is turned on, and a leakage current is smaller and current leakage occurs seldom when the oxide TFT is turned off).
The oxide TFT with a back channel etch (BCE) structure has been widely used due to such advantages as a simple structure, a simple manufacturing process, a small size and a small parasitic capacitance. As shown in FIG. 1, a source electrode 1 and a drain electrode 2 are directly lapped onto an oxide semiconductor layer 3. To be specific, the oxide semiconductor layer 3 is formed at first, then a source/drain metal film is formed on the oxide semiconductor layer 3, and then the source/drain metal film is etched by a photolithographic process so as to form the source electrode 1 and the drain electrode 2. For the photolithographic process, it is required to etch off the source/drain metal film between the source electrode 1 and the drain electrode 2, so obviously the oxide semiconductor layer 3 therebetween will be corroded due to an etchant, and thereby a semiconductor characteristic of the TFT will be adversely affected.
In order to overcome the above drawbacks, in the related art, an etch stop layer 102 is arranged on the oxide semiconductor layer 3, and the source electrode 1 and the drain electrode 2 are in electrical contact with the oxide semiconductor layer 3 through a via-hole in the etch stop layer 102. However, an additional photolithographic process is desired for the etch stop layer 102, so the production cost will be increased. In addition, an aperture ratio will be adversely affected due to the via-hole in the etch stop layer 102.